Conventional enterprise storage arrays are commonly power aware (or power efficient) to address the overall increase in data center power specifications. One conventional power efficiency technique is to monitor an activity span (i.e., active/idle) during an array operation. Certain functional blocks are placed in identified low power states (i.e., a serial-ATA link partial/slumber).
Considerable power consumption differences exist between a physical layer device (i.e., PHY) driving an interface at a fastest supported speed versus a next fastest supported speed. According to the Small Computer Serial Interface (i.e., SCSI) Trade Association, power ratings are 20% less for a serial attached SCSI (i.e., SAS) PHY signaling at 6 gigabits per second (i.e., Gbps) versus 3 Gbps. For a x4 SAS port, the compared data is expected to be even less while operating the link at 1.5 Gbps.
A power bandwidth ratio is a functional aspect of storage arrays that are being closely driven in the industry. The bandwidth ratio (i.e., watts/bandwidth) is defined as the power in watts dissipated while achieving a bandwidth in Gbps. The interfaces drive the data at a high raw bandwidth while the effective data rate achieved is largely determined by the application load from the host and back-end components within a storage array. Most applications do not saturate the available raw bandwidth of the storage interface.
It would be desirable to implement a storage array that reduces interface signaling speeds when an application could use a slower speed without performance degradation. The reduced speed may reduce overall power consumption in an effort toward achieving environmentally friendly storage.